This application relates to a switch mechanism for use in a laryngoscope handle.
In a known type of laryngoscope such as that disclosed in U.S. Pat. Nos. 4,556,052 and 4,273,112, which are incorporated herein by reference, the laryngoscope consists of a handle portion and a blade portion. The blade is movable between a rest or storage position in which it is substantially parallel to the handle, and a working position in which it is substantially perpendicular to the handle. In the working position, an optical fiber in the blade is aligned with a light source within the handle. Further placement of the blade into the working position activates a switch to energize the light source, such that light passes through the optical fiber to illuminate the area surrounding the distal end of the blade when the blade is in the working position.
Various designs have been disclosed for the switch which is activated when the laryngoscope blade is placed into the working position. One such design is shown in FIG. 4. As shown, a lamp 7 is mounted in a slidable mounting sleeve 21 and within a blade sleeve 8. A spring 101 presses the mounting sleeve 21 upward away from the a contact plunger 102. The contact plunger 102 is pressed upward by a second spring 103 relative to a contact terminal 104 which is screwed into insulating barrel 25. When the blade is swung into the working position, it presses on the blade sleeve 8, causing the blade sleeve 8, lamp 7 and mounting sleeve 21 to move in a downward direction against force of spring 101. This causes the base terminal 105 of the lamp 7 to come into contact with the contact plunger 102. The contact plunger 102 is in turn in electrical contact with the contact terminal 104 via the second spring 103.
While the switch mechanism shown in FIG. 4 works to turn the lamp on and off in response to the position of a blade attached to the handle, it is not without its drawbacks. In particular, the indirect contact between the contact plunger and the contact terminal can introduce problems if spring 103 breaks, or becomes disconnected from one of the two contact points, leading to intermittent flow of electrical current through the switch. Furthermore, the contact terminal 104 is always held in contact with the positive terminal of the upper most battery by the conical spring which acts as an electrical contact 3 at the base of the housing.